This invention relates to a system for preventing the collision of two cutting tools in a computer-controlled cutting unit, wherein the two cutting tools may at times be moved toward each other.
German Unexamined patent application OS 3,321,954 (equivalent to U.S. Pat. No. 4,463,639) discloses an ultrahigh-pressure water-jet cutting unit with a cutting system consisting of a cutting portal and a cutting-head support located thereon. The contours to be cut out of the material by the high-pressure jet located in the cutting-head support are entered manually into a computer connected to the cutting system, in the form of data comprising pairs of coordinates, and are then cut out individually with the high-pressure jet open.
Various systems have been proposed in an attempt to shorten the processing time required to carry out cutting operations on such a machine.
Particularly in the case where several patterns are to be cut out of a blank, procedures are disclosed in German Patent No. 3,544,251 (equivalent to U.S. Pat. No. 4,901,359) and German Unexamined patent application OS 3,627,110 (equivalent to U.S. Ser. No. 07/070,902 filed July 8, 1987, now U.S. Pat. No. 4,941,183) by means of which a rapid layout of the cutting patter becomes possible and, at the same time, the contours of the individual patterns and their positions are automatically reported to the computer. Then, in each case, these contours are cut out in the sequence in which they were received by the computer. With this procedure, however, only the portions of the processing time that previously depended on the speed of the operating personnel, namely the pattern layout and the contour data input, are improved.
In order to reduce the processing time required to cut material in accordance with several patterns from a web of fabric or a large plate-shaped material on a computer-controlled cutting unit, several cutting tools can be used simultaneously for the cutting process.
If two cutting tools are used, they can be arranged in such a way that, starting the cutting simultaneously from the outer edge of the cutting table of the cutting unit, they move toward each other and each cuts along one-half of each predetermined cutting line in the longitudinal and transverse directions.
To prevent a collision in the center of the cutting table of the cutting portals which receive the cutting tools, it is also conceivable to start the cutting from the center and to terminate it at the edges.
To increase the utilization factor (the ratio of the area of the material cut out, to the area of the original fabric web), one of the cutting tools is desirably moved from the center toward the outside and the other from the outside into the interior region, so that a seamless transition of the cutting lines can be achieved in this way.
With all of the previously mentioned procedures, the cutting time can be reduced by a factor corresponding to the number of cutting tools used, as compared with the cutting time required by a single tool. However, this can be achieved only when the cut is symmetrical with respect to the line on which the starting point and end point of the individual cutting tools is located. For an unsymmetrical cut, the time reduction depends exclusively on the contours of the individual patterns that are to be cut out.